The diameter of a brand of tennis balls is approximately normally distributed, with a mean of 2.60 inches and a standard deviation of 0.03 inch. Suppose that you randomly sample 9 tennis balls. (a) What is the mean of the sampling distribution and the standard error of the mean? (b) What is the probability that the sample mean is between 2.61 and 2.63 inches? (c) The probability is 80% that the sample mean will be between what two values symmetrically distributed around the population mean